We thank Franco and Bronson for their interest in our article.1 They raise the possibility that depression may play a role in the relation of diabetes mellitus to risk of Alzheimer disease (AD) and to cognitive decline. To address this possibility, we repeated the analyses after excluding 11 persons with clinically diagnosed depression at the baseline evaluation and then following exclusion of 65 persons who had a clinical diagnosis of depression at any point in their lifetime. In both sets of analyses, the relation of diabetes mellitus to risk of AD (for both analyses: hazard ratio, 1.70 [95% confidence interval, 1.13-2.56]) and to decline in perceptual speed (P<.05) were unchanged, suggesting that clinical depression does not account for these associations. Whether the much more common mild depressive symptoms, which are related to AD,2 could be associated with diabetes mellitus requires further exploration.
Arvanitakis Z, Wilson RS, Bennett DA. Diabetes Mellitus and Alzheimer Disease—Reply. Arch Neurol. 2005;62(2):330-331. doi:10.1001/archneur.62.2.330-b